Varicella zoster virus (VZV) causes childhood varicella (chickenpox), becomes latent in ganglionic neurons at all levels of the neuraxis and reactivates decades later to cause zoster (shingles) and postherpetic neuralgia (PHN), especially in the elderly. Although a zoster vaccine is available, even if every adult in the U.S. >60 years were vaccinated, there would still be -500,000 zoster cases annually, about 200,000 of whom will experience PHN, stroke, blindness or myelopathy caused by VZV reactivation. An alternative to vaccination is prevention of virus reactivation based on an in-depth understanding of the physical state of viral nucleic acid and gene expression during latency and their changes during reactivation. We and others have shown that VZV IE63, the immediate early (IE)protein encoded by open reading frame 63, is a consistent hallmark of VZV latency. Based on the fact that IE63, a predominantly nuclear phosphoprotein during productive infection, is located exclusively in the cytoplasm of latently- infected neurons where its phosphorylation state is unknown, we hypothesize that translocation of IE63 from the cytoplasm to the nucleus results in altered IE63 function and initiation of virus reactivation. We will test this hypothesis by identifying cytoplasmic and nuclear forms of IE63 and their functions in neuronal and non-neuronal cells in culture (Aim1), the cellular location of IE63 in human ganglia during virus reactivation (Aim2), and the pattern of VZV gene transcription and their epigenetic regulation during reactivation in explanted human trigeminal ganglia (Aim3). These studies will provide the first comprehensive picture of VZV reactivation in humans. We are uniquely qualified to carry out these studies since we have a continuous supply of human ganglia obtained at autopsy, have shown that ganglia from more than 90% of humans are latently infected with VZV,that VZV reactivation occurs after explantation, and that optimized GeXP technology detects low-abundance VZV gene transcripts. Further, we have constructed recombinant mouse anti-IE63 antibodies that recognize nuclear or cytoplasmic forms of IE63. Our in-depth analysis of the mechanism of VZV reactivation in human TG will identify new targets for therapeutic intervention to prevent virus reactivation.